I. Field of the Invention
The present invention relates generally to the fields of molecular biology, RNA interference, and oncology. More particularly, the invention concerns compositions comprising an siRNA (or nucleic acid encoding an siRNA) and a lipid component, wherein the siRNA is targeted to a nucleic acid encoding an interleukin. The invention also generally pertains to methods of treating cancer in a subject involving administering to the subject an IL-8 antagonist.
II. Description of Related Art
Ovarian cancer remains a significant cause of death among women in the United States. Recurrence of cancer following treatment of primary disease with surgery and chemotherapy is common. Thus, there is the need for new therapeutic agents in order to improve survival rates and eventually cure patients from this deadly disease.
Interleukin-8 (IL-8) is a potent pro-angiogenic cytokine that is known to be overexpressed in human cancers, including ovarian carcinoma (Lokshin et al., 2006; Xie, 2001; Kassim et al., 2004, and Koch et al., 1992). IL-8 is a small (8 kDa) molecule secreted by multiple sources including monocytes, neutrophils, endothelial and mesothelial cells and is predominantly responsible for recruitment of neutrophils, T-cells, and basophils during immune system activation (Walz et al., 1987; Schroder and Christophers, 1986; Matsushima and Oppenheim, 1989). Activators of IL-8 include tumor necrosis factor-alpha (TNF-α) and interleukin-1β (IL-1β) (Matsushima and Oppenheim, 1989), acute infections (Roebuck, 1999), and external factors, such as chemicals, chemotherapeutic agents, UV light, and stressful environments resulting in hypoxia and acidosis (Xie, 2001; Roebuck, 1999; Xu et al., 1999; Xu and Fidler, 2000; Lee et al., 1996). The induction of IL-8 expression is mediated by factors including nuclear transcription factor, NF-κB; however, recent studies have shown that IL-8 expression can increase following activation of the Src/STAT3 pathway, independent of NF-κB involvement (Trevino et al., 2006).
IL-8 acts by binding to the seven-transmembrane, G-protein coupled receptors, CXCR1 and CXCR2. Both of these receptors are expressed on a majority of tumor cell types as well as human endothelial cells (Murdoch, 1999; Xu and Fidler, 2000). Previous studies have shown that increased IL-8 expression in vivo leads to enhanced tumor growth, angiogenesis, and metastases (Xu and Fidler, 2000; Karashima et al., 2003; Luca et al., 1997; Kim et al., 2001). In addition, IL-8 increased human endothelial cell proliferation, tubule formation, and survival (Li et al., 2005). Further, blocking IL-8 activity has been shown to lead to decreased tumor growth, microvessel density, and distant metastases (Huang et al., 2002; Mian et al., 2003). Ovarian cancer expresses high levels of IL-8 which has been shown to be associated with poor clinical outcome (Kassim et al., 2004).
Since its initial description in C. elegans (Fire, 1998) and mammalian cells (Elbashir et al., 2001), use of short interfering RNA (siRNA) as a method of gene silencing has rapidly become a powerful tool in protein function delineation, gene discovery, and drug development (Hannon, 2004).
Liposomes have been used previously for drug delivery (e.g., delivery of a chemotherapeutic). Liposomes (e.g., cationic liposomes) are described in PCT publications WO02/100435A1, WO03/015757A1, and WO04029213A2; U.S. Pat. Nos. 5,962,016, 5,030,453, and 6,680,068; and U.S. Patent Application 2004/0208921, all of which are hereby incorporated by reference in their entirety without disclaimer. A process of making liposomes is also described in WO04/002453A1. Furthermore, neutral lipids have been incorporated into cationic liposomes (e.g., Farhood et al., 1995).
Cationic liposomes have been used to deliver siRNA to various cell types (Sioud and Sorensen, 2003; U.S. Patent Application 2004/0204377; Duxbury et al., 2004; Donze and Picard, 2002). However, it is not clear if or to what degree neutral liposomes may be used deliver siRNA to a cell.
Neutral liposomes have been tested to a limited degree. Miller et al. (1998) evaluated the uptake of neutral unilamellar liposomes; however, this work observed that cationic liposomes are taken up by cells more efficiently than neutral liposomes, thus teaching away from the idea that neutral liposomes may be more effective than cationic liposomes. Neutral liposomes were used to deliver therapeutic antisense oligonucleotides in U.S. Patent Application 2003/0012812 and siRNA in WO 2006/113679.